The present invention relates to a cell design used in a trawl system associated with capturing marine life within a body of water, and more particularly to an improved cell design (that by definition is iterated or cloned in varying geometric patterns) providing improved shaping and performance, especially when incorporated in midwater or bottom trawls of such systems.
In one aspect, the invention relates to mesh cell construction for trawls that can be triangular, rectangular and/or hexagonal in cross section (where such rectangular configurations include square cells) and is associated with at least three and preferably four cell (or more) bars in a common plane, with the length of each bar being measured between a pair of normalized transverse, quasi-transverse, longitudinal or quasi-longitudinal spaced-apart knots or equivalent couplers. In accordance with the invention, a pair of half mesh bars of each cell are constructed so as to fan out from a common knot or coupler (of the four knots or couplers associated with each quadratic mesh cell). Each mesh bar of such pair is constructed to provide hydrofoil-like characteristics in field operations. Each mesh bar comprises two (or three of more) strands each comprised of filamented synthetic material such as plastic or of a naturally occurring substance, each strand being the product of a conventional manufacturing process. In accordance with the invention, such the strands are constructed to be loosely twisted about a longitudinal axis of symmetry in a direction opposite (not the same) as its mating mesh bar. In addition, the pitch of the twist is controlled wherein each mesh bar defines a a range of pitch value, say from 3 d to 70 d and preferably 5 d to 40 d where d is the diameter of at least the smaller of the twisted strands. In another aspect, each mesh bar comprises a strap of synthetic or natural fibers of either rectangular, or quasi-rectangular cross section, preferably twisted along its longitudinal axis of symmetry whereby in operation the short sides form interchanging leading and trailing edges. In still another aspect, the invention relates to cell construction associated with tow, bridle and breast lines that attach to the trawl and improved performance thereof. Result: rather deep grooves are formed along the length of each cell bar that interact with passing water during operations as explained below. Note in this regard that the invention provides for a cell construction that can be systemized. In the case of a trawl, the opposite mesh bars of any rectangularly shaped mesh cell act as mini-hydrofoils or wings in concert in operations. Such opposite bars (whether formed of a series of twisted strands or of a single twisted strap), are characterized as having a common lay direction when viewed in an axially receding direction (either right-handed or left-handed lay) that is opposite to that associated with the remaining opposite mesh bars of such mesh cell.
When incorporated in a trawl system, such cell construction of the invention, provides for improved shaping and performance. That is, the cells positioned at different geometrical locations relative to and about the longitudinal central axis of the trawl, can be controlled such that resulting trawl panels, wings, bridle lines, towlines etc., act analogous to a series of mini-hydrofoils capable of acting in concert in operation. Such concerted action providesxe2x80x94when the trawl is in motionxe2x80x94outwardly directed force vectors which increasexe2x80x94significantlyxe2x80x94trawl system performance characteristics including but not limited to overall trawl volume while simultaneouslyxe2x80x94and surprisinglyxe2x80x94decreasing drag and background noise.
It is well understood that the basic cell of a selected portion of every trawl system net is the unit cell (called cell hereinafter). The selected portions of the trawl system is then built by repeating the basic shape.
It is axiomatic that the ability to predict the overall shape and performance of the finished product depends entirely on the shape and structural integrity of that single cell. Heretofore, proper trawl making was a two-step process that involved initial construction of undersized mesh cells, and setting the knots and mesh sizes by the substeps of depth stretching and heat setting involving turning the finished mesh in direction opposite to its natural bent and applying pressure, and then applying heat to set the knots.
Materials used in the mesh cell construction can be plastics such nylon and polyethylene but other type of natural occurring fibers also can be (and have been) used. Single, double (or more) strands make up a thread or twine composed of, say, nylon, polyethylene and/or cotton. Additionally, braided cords, of natural and synthetic materials, as well as rope and cables, have been used. However, the pitch of any braided or twisted thread, twine, cord and/or rope (distance between corresponding points along one of the strands constituting one turn thereof) which is analogous to the pitch between corresponding screw threads), has been small. Moreover, modem manufacturing processes use threads. twines, cords, cables or ropes to form mesh cells, and have always produced cells in which twist direction of the individual bars comprising each cell, is always the same. None have proposed the use of differently oriented twist of individual mesh bars of the mesh cell in the manner provided by the instant invention.
Even though various Japanese Patent Applications superficially deal with nets having differing twist directions, (see for example, Jap. Pat. Apps. 57-13660, 60-39782 and 61-386), these deal with a contrary goal than that of the instant invention, viz., to a balancing of residual torque forces within the net structure during construction thereof, not to the generation of composite vector forces during actual field operations (via water flow-net shape interaction) for enhancement of net performance. The first-mention Application, for example, states that its purpose is to provide xe2x80x9cnet legs with different twist directions according to a fixed regular pattern so that torsion and torque of said net legs are mutually canceledxe2x80x9d and must generate substantially inconclusive unbalanced forces during operations since the depicted net would lead to a shrinkage in net volume, not increasing net volume as provided by the instant invention.
The present invention is based on the discovery that individual bars of a cell can be controlled to act as mini-hydrofoils in operation. In one aspect, the invention controls twist direction, either right-handed or left-handed in a receding direction from a knot or equivalent coupler, in a fashion to provide for an improved shaping and performance of resulting trawl system.
In one aspect, the invention relates to mesh cell construction for trawls that can be triangular, rectangular and/or hexagonal in cross section (where such rectangular configurations include square cells) and is associated with at least three and preferably four cell (or more) bars in a common plane, with the length of each bar being measured between a pair of normalized transverse, quasi-transverse, longitudinal or quasi-longitudinal spaced-apart knots or equivalent couplers. In accordance with the invention, a pair of half mesh bars of each cell are constructed so as to fan out from a common knot or coupler (of the four knots or couplers associated with each quadratic mesh cell). Each mesh bar of such pair is constructed to provide hydrofoil-like characteristics in field operations. Each mesh bar comprises two (or three or more) strands comprised of filamented synthetic material such as plastic or naturally occurring substance, each strand being the product of a conventional manufacturing process. In accordance with the invention, such the strands are constructed to be rather loosely twisted about a longitudinal axis of symmetry in direction that is opposite (not the same) direction as its mating mesh bar. In addition, the pitch of the twist is controlled wherein each mesh bar defines a range of pitch values, say from 3 d to 70 d with 5 d to 40 d being preferred where d is the diameter of at least the smaller of the twisted strands. In additio, each mesh bar can comprise a strap of synthetic or natural fibers of rectangular, quasi-rectangular cross section, preferably twisted along its longitudinal axis of symmetry whereby in operation the short sides form interchanging leading and trailing edges. In still another aspect, the invention relates to cell construction associated with tow, bridle and breast lines that attach to the trawl and improved performance thereof Result: rather deep grooves are formed along the length of each cell bar that interact with passing water during operations as explained below. Note in this regard that the invention provides for a cell construction that can be systemized. In the case of a trawl, the opposite mesh bars of any rectangularly shaped mesh cell act as mini-hydrofoils or wings in concert in operations. Such opposite bars (whether formed of a series of twisted strands or of a single twisted strap), are characterized as having a common lay direction when viewed in an axially receding direction (either right-handed or left-handed lay) that is opposite to that associated with the remaining opposite mesh bars of such mesh cell.
When incorporated in a trawl system, such cell construction of the invention, provides for improved shaping and performance. That is, the cells positioned at different geometrical locations relative to and about the longitudinal central axis of the trawl, can be controlled such that resulting trawl panels, wings, bridle lines, towlines etc., act analogous to a series of mini-hydrofoils capable of acting in concert in operation. Such concerted action providesxe2x80x94when the trawl is in motionxe2x80x94outwardly directed force vectors which increasexe2x80x94significantlyxe2x80x94trawl system performance characteristics including but not limited to overall trawl volume while simultaneouslyxe2x80x94and surprisinglyxe2x80x94decreasing drag and background noise.
MESH is one of the openings between threads, ropes or cords of a net;
MESH CELL means the sides of a mesh and includes at least three sides and associated knots or equivalent couplers oriented in space. For a quadratic cell a longitudinal working plane bisects the knots or couplers and sides and defines a rectangular (including square) cross section with four sides and four knots or couplers. For a triangular cell, the longitudinal working plane defines a triangular cross section with three sides and three knots or couplers. For a hexagonal cell, the longitudinal working plane defines a hexagonal cross section with six sides and six knots or equivalent couplers;
MESH BARS means the sides of a mesh cell;
CELL means a construction unit of a trawl, net or the like and includes both a mesh cell relating to enclosable sides of the mesh of the trawl or net itself, as well as to bridle, breast and tow lines used in transport of the trawl or net through a water column to gather marine life.
CELL BAR means both the sides of a mesh cell and the elements that make up the bridle, breast and tow lines.
RIGHT- AND/OR LEFT-HANDINESS IN A RECEDING DIRECTION along a cell bar relates to the establishment of a central axis of the trawl, net or the like for which the cell associated with the cell bar relate, then with a normalized imaginary giant stick figure positioned so that his feet intersect said central axis but rotatable therewith and his back positioned to first intersect the velocity vector of the moving trawl, net or the like associated with cell, determining right- and/or left-handiness of the cell bar using the location of either of right or his left arm of the such giant stick figure irrespective of the fact that the cell bar position relative to the central axis may be either above, below or offset therefrom, wherein the giant figure always rotates about the central axis and his arms penetrate through the cell bar.
HALF OF MESH CELL means one-half of the cell of the invention is defined by a transverse working plane normal to the longitudinal plane that passes through the centroid of each mesh cell. For the quadratic cell, the transverse working plane passes through two transverse knots or couplers and forms the base of the half mesh cell and each half mesh cell includes a central knot or coupler and two mesh bars consisting of two mesh bars. Each mesh bar comprises a thread having hydrofoil characteristics in operation.
THREAD or MESH BAR are equivalent mesh units and is composed of, in accordance with the invention, of synthetic or natural fibers having hydrofoil-like characteristics in field operation. Firstly, a thread can comprise two strands twisted along the longitudinal axis of symmetry in a loose fashion, say where the pitch is in a range of 10 d-70 d where d is the diameter of the larger of the strands or where d is their diameters if the same. Or secondly, a thread can comprise a strap of solid geometric configuration, say composed of fibers having hydrofoil-like characteristics in operation.
STRAP is a flexible element of synthetic or natural fibers that forms a mesh bar, the strap having a cross section that is generally rectangular or can be quasi-rectangular with rounded short sides and elongated long sides with or without camber. In operation, the strap acts as a hydrofoil, preferably twisted along its longitudinal axis wherein the short sides form interchanging leading and trailing edges. Or where the strap is not twisted, the long sides can be shaped relative to each to provide a pressure differential therebetween resulting in hydrofoil-like effects.
PRODUCT STRAND includes the synthetic or natural fibers or filaments used to form the construction unit of the invention which is preferably but not necessarily the product of a conventional manufacturing process, usually made of nylon, polyethylene, cotton or the like twisted in common lay direction. Such strand can be twisted, plaited, braided or laid parallel to form a sub-unit for further twisting or other use within a mesh bar or a cell bar in accordance with the invention.
NET is a meshed arrangement of threads that have been woven or knotted or otherwise coupled together usually at regular intervals or at intervals that vary usually uniformly along the length of the trawl.
TRAWL is a large net generally in the shape of a truncated cone including bridle lines and like means to keep its mouth open and towlines to enable same to be trailed through a water column or dragged along a sea bottom to gather marine life including fish.
CODEND is a portion of a trawl positioned at the trailing end thereof and comprises a closed sac-like terminus in which the gathered marine life including fish are trapped.
FRAME is a portion of the larger sized meshes of a net or trawl upon which is overlaid (and attached by a binding) a netting of conventional twist.
PANEL is one of the sections of a trawl and is made to fit generally within and about frames shaped by riblines offset from the longitudinal axis of symmetry of the trawl.
PITCH is the amount of advance in one turn of one strand twisted about another strand (or strands) when viewed axially. Or common advance of the twist of the strap along its axis of symmetry.
LAY is the direction in which the strands or the strap wind when viewed axially and in a receding direction.
INTERNAL LAY OR TWIST is the direction of synthetic or natural fibers comprising each product strand, is wound when viewed axially and in a receding direction.
INTERNAL BRAID describes the method of formation of a particular product strand.
TOW LINE comprises a cable, rope or the like that connects a vessel at the surface of a body of water with the trawl, net or the like. Such connection can bia via a trawl door and thence through a bridle to the frontropes attached at the mouth of the trawl, net or the like. In the absence of doors, the tow line can connect directly to a bridle. A vessel or trawler usually employs two towline, one positioned at the portside and one nearer the starboard side.
FRONTROPE(S) is a term that includes all lines located at perimeter edge of the mouth of the trawl, net or the like, such as headrope, footrope (or bottomrope) and breast lines. The frontropes have a number of connections relative to each other and to the bridle lines.
BRIDLES relates to lines that intersect the frontropes and attach to the tow lines. For a particular port or starboard tow line, a pair of bridles extend from a common connection point therewith, back to the frontropes.
TRAWL SYSTEM is a term that includes the trawl, net or the like in association with the tow lines therefor as well as the frontropes and bridles lines.